Ferrari have been accused of spying on Formula One rivals McLaren by former head of development Nigel Stepney.

In the latest twist to the "spy-gate" saga, Stepney claims he received key information about McLaren's set-up.

"I got weight distribution, I got other aspects of various parts of their car, and I was Ferrari's employee at the time," he told grandprix.com.

Stepney was sacked by Ferrari in July, and a team spokesman dismissed his claims as "not credible".

"We cannot take into consideration quotes from a man like him," the spokesman added, "a man who gave 780 pages of Ferrari documents to the chief designer of McLaren, who exchanged 320 e-mails and SMS messages with him.

"Can he sound credible talking about that?"

McLaren were fined £49.2m and stripped of the constructors points for the 2007 season following a World Motor Sport Council hearing in Paris last month after being found guilty of possessing confidential Ferrari information.

But Stepney believes Ferrari's conduct should also have been questioned.

It was Coughlan's sharing of similar information about Ferrari with drivers Fernando Alonso and Pedro de la Rosa that led the World Motor Sport Council of F1's governing body the FIA to punish McLaren last month.

And Stepney added: "I was aware of certain stuff they [McLaren] were doing at tests, fuel levels for example. I think Ferrari should have been docked points personally.

"The question is: did I use the information, did I talk about it? I spoke to some people [at Ferrari] about it. I can't prove it, there are no e-mails or anything; points about the fuel and the differences between the teams were discussed inside.

"But as well as McLaren having an advantage, did Ferrari have an advantage? I think so.

"It looks like information was flowing only one way. No one has been balancing the argument, no one has asked the question."

In another twist, the BBC has seen a copy of a letter from Stepney to FIA president Max Mosley in which he claims he told the governing body about his concerns surrounding a part of the Ferrari car before the start of the season.

McLaren used that knowledge as part of their defence to the World Council, claiming Stepney had informed them about what he perceived to be an illegal floor on the Ferrari in a legitimate attempt at "whistle-blowing".

Stepney says in the letter that he communicated his concerns to FIA technical adviser Peter Wright first by telephone and then e-mail, and only passed them to Coughlan later on.

At the hearing, which was on 13 September, Mosley dismissed McLaren's claims, saying: "If there was any hint of whistle-blowing, it was not in those documents [e-mails to Wright and FIA race director Charlie Whiting].

"He had the opportunity to whistle-blow at the beginning. He did not. Instead, he communicated the information to McLaren.

"The fact is that he did not give us information, despite being in touch with our people."

The part of the floor Stepney had questioned was declared illegal following a request for clarification from McLaren after Ferrari driver Kimi Raikkonen had won the Australian Grand Prix.

Mike [Coughlan, McLaren's chief designer] really had no reason to use any of this information at McLaren and to the best of my knowledge he never contemplated the idea

Nigel Stepney

The result from Melbourne, where McLaren drivers Fernando Alonso and Lewis Hamilton finished second and third, was not changed.

Stepney also describes in the letter - the full text of which has been published on grandprix.com - how McLaren chief designer Mike Coughlan came into possession of the 780 pages of confidential Ferrari information that led to the team's punishment.

Stepney said he had been discussing a new direction in his career with Coughlan, who is an old friend from their time at Benetton and Ferrari in the 1980s and 1990s.

Stepney said Coughlan took the documents at a meeting they had in Barcelona in April, but added: "He told me: 'Don't worry, I won't use any of this stuff.'

"Mike really had no reason to use any of this information at McLaren and to the best of my knowledge he never contemplated the idea.

"You cannot take items from one concept of car design, manufacture them and expect that they are going to benefit the concept of another car design.

"There was never any intention of using this information in any other team."